The invention relates to a method for profiling the broad sides of a flat reversible key, a key blank being clamped in a clamping device in such a way that the first broad side of the key blank is exposed, complementary grooves and ribs being milled using a milling cutter that has cutter teeth on its peripheral surface and rotates about a cutter shaft, by advance in the longitudinal direction of the key with respect to the longitudinal section profile of the cutter teeth, and the key blank then being clamped in a position which is turned by 180° about the longitudinal axis of the key in such a way that the second broad side of the key blank is exposed, and complementary grooves and ribs being milled into the broad side, using the same milling cutter, by advance in the longitudinal direction of the key with respect to the longitudinal section profile of the cutter teeth.
The invention further relates to a flat reversible key profile for a flat reversible key to be produced according to the method, the key having a key bit which has a first broad side and a second broad side situated opposite therefrom, the two broad sides forming grooves and ribs which extend symmetrically, in the cross-section, about a single point, relative to a longitudinal central axis of the key.
The invention further relates to a flat reversible key which has been produced corresponding to the profile variation specification according to the invention, and which is part of a locking system.
Flat keys produced according to such a method have an elongate key shank whose broad sides are profiled with alternating grooves and ribs. The ribs and grooves extend in the direction of the longitudinal extent of the key shank. At one end, the key shank has a key tip via which the key may be inserted into a profiled key channel, which is substantially complementary to the key profile, of a lock cylinder. The key shank originates from a key bow at the end opposite from the key tip. Such flat keys have two narrow sides and two broad sides. In the cross-section through the key shank, the broad sides are configured symmetrically about a single point relative to a longitudinal centerline, so that the flat reversible key may be inserted in two reversed positions into a key channel of a lock cylinder. Each of the two broad sides is thus identically profiled with grooves and ribs which extend parallel to the centerline of the key. The key channel forms complementary grooves and ribs, so that in this region grooves and ribs of the key and of the walls of the key channel interengage in a guiding manner. The portion of the key shank having the indentations is likewise provided with ribs and grooves which may have different rib heights and groove depths in order to individualize keys or locking systems. Locking hierarchies are developed by adding or removing grooves or ribs.
A generic method for producing a key of this kind is disclosed in DE 10 2007 057 407 A1. As described therein, the key blank is clamped between two clamping jaws so that one of the two broad sides is exposed. The broad sides are profiled using a milling cutter having cutter teeth on its peripheral surface which have a profile that is complementary to the profiled grooves and profiled ribs of the key shank being produced. The key is advanced in the direction of extent of the shank. The axes of the milling cutters which are rotationally driven by an electric motor extend parallel to the plane of the broad side of the key. This means that these axes extend perpendicularly to the surface normals of the plane of the broad side.
A similar device which may be used to carry out the generic method is disclosed in DE 100 49 662 C2. Here as well, grooves and ribs are milled parallel to the direction of extent of the key, using a milling cutter which is rotationally driven about a rotational axis that extends parallel to the plane of the broad side of the key. This method may be used to mill only grooves or ribs whose groove walls or rib walls, respectively, define a positive angle relative to the key normals. The flank angles of the cutter tooth ribs are greater than 90°. Therefore, the flank angles of the grooves are also greater than 90°. The magnitude of the clearance angle relative to the vertical is usually 3° in order to avoid harmful friction of the cutter teeth against the groove walls.
DE 694 21 093 T2 describes the production of undercut profiled grooves on a key blank, using cutting discs which are driven about rotational axes that are inclined with respect to the plane of the broad side of the key.
It is known from DE 35 42 008 to produce undercut grooves by applying a disc to the broad side of a key.
DE 33 14 511 A1 describes a flat key, wherein grooves having an undercut groove wall are cut on each of two oppositely situated broad sides.
A key profile is likewise known from DE 10 2005 036 113 A1, wherein groove walls of the profiled grooves are undercut. Here as well, the undercut grooves must be milled in a separate work operation, using inclined cutting discs.